The present invention relates generally to a chip type semiconductor device, and more particularly to a surface mountable chip type semiconductor device which has high moisture resistance and which has thin and small device shape.
It is required that small type and portable electronic circuit apparatuses, for example, a video camera, a personal computer, a portable telephone and the like, are compact and lightweight. Therefore, it is also required that electronic parts or components used in such electronic circuit apparatuses are compact and lightweight. As an electronic component which fulfills such requirements, there is known a chip type semiconductor device disclosed in Japanese patent laid-open publication No. 6-125021 (prior art 1). FIG. 17 shows a cross sectional structure of the chip type semiconductor device which is generally designated by a reference numeral 6 in the drawing and which is disclosed in Japanese patent laid-open publication No. 6-125021.
In FIG. 17, a reference numeral 1 designates a semiconductor pellet which constitutes the main portion of the electronic component. The semiconductor pellet 1 has electrodes (not shown in the drawing) formed on both surfaces thereof. A reference numeral 2 designates an island portion on which the semiconductor pellet 1 is mounted. Reference numerals 3a and 3b designate lead portions. One end of the lead portion 3a is electrically connected to the island portion 2. The other lead portion 3b is disposed such that one end of the lead portion 3b is located in the proximity of the island portion 2. Outer ends of both lead portions 3a and 3b extend outside. Reference numeral 4 designates a wire which electrically couples an electrode (not shown in the drawing) on the semiconductor pellet 1 and the lead portion 3b. Reference numeral 5 designates an encapsulation resin portion which encapsulates a main portion of the semiconductor device 6 including the semiconductor pellet 1 and the like.
In the semiconductor device 6, each of the lead portions 3a and 3b are bent within the encapsulation resin portion 5 into a crank shape approximately at the middle portion thereof. Also, a portion from the middle portion to the outer end portion of each of the lead portions 3a and 3b is exposed from the encapsulation resin portion 5 and extracted outside along the bottom surface 5a of the encapsulation resin portion 5. The outer end portion of each of the lead portions 3a and 3b is cut in the proximity of a corresponding side wall of the encapsulation resin portion 5. In the semiconductor device shown in FIG. 17, the portions from the middle portions to the outer end portions of the lead portions 3a and 3b which are exposed from the encapsulation resin portion 5 are set to become approximately coplanar. Therefore, the semiconductor device shown in FIG. 17 can be surface mounted stably on a wiring substrate and the like.
The semiconductor device shown in FIG. 17 is fabricated by using a lead frame (not shown in the drawing) which integrally includes the island portion 2 and lead portions 3a and 3b. In order to obtain a compact and thin semiconductor device, it is necessary to use the lead frame which is made of a thin material and which is minutely worked into desired patterns. Also, it is necessary to reduce the loop height of the wire 4. However, the minutely worked lead frame deforms easily and it is difficult to handle such lead frame. Further, when the loop height of the wire 4 is kept low, there is a possibility that the wire 4 comes close to or contacts the corner portion of the semiconductor pellet 1 and the like and, thereby, deteriorating electrical isolation between the wire 4 and other portions of the semiconductor device or short-circuiting therebetween.
In the above-mentioned Japanese patent laid-open publication No. 6-125021 (prior art 1), there is also disclosed another chip type semiconductor device, which is shown in FIG. 18. In the semiconductor device shown in FIG. 18, instead of using the wire 4 used in the semiconductor device of FIG. 17, the semiconductor pellet 1 is inserted directly between lead portions 3a and 3b. However, since both the semiconductor pellet 1 and the lead portions 3a and 3b are minute, fabrication process becomes complicate and difficult. Also, after mounting the semiconductor pellet 1 on an island portion 2 of the lead portion 3a and electrically coupling the semiconductor pellet 1 with the lead portions 3a and 3b, undesired portions of the resin molded lead frame are cut away and a separate semiconductor device is obtained. In this case, if the lead portions 3a and 3b are cut in the proximity of an encapsulation resin portion 5, there is a possibility that cracks are produced in the encapsulation resin portion 5, and that lead portions 3a and 3b and the encapsulation resin portion 5 are delaminated at the interface therebetween and, thereby, moisture resistance of the semiconductor device is deteriorated. Therefore, it was impossible to cut the lead portions 3a and 3b in the proximity of the side wall portions of the encapsulation resin portion 5, and it was impossible to reduce the outer size of the semiconductor device much.
Japanese patent laid-open publication No. 7-169766 (prior art 2) discloses a semiconductor device which can be made thinner than the semiconductor device shown in FIG. 18. In the semiconductor device of the prior art 2, a semiconductor pellet is wholly molded by resin except electrode portions such that the electrode portions of the semiconductor pellet are exposed. Thereafter, projected electrodes are formed on the exposed electrode portions of the semiconductor pellet. However, in the semiconductor device having such structure, when the semiconductor pellet is molded by resin, it was difficult to precisely locate the semiconductor pellet within a metal molding die such that the electrode portions of the semiconductor pellet come into contact with protruded portions of inner wall of the metal molding die. It was also difficult to resin mold the semiconductor pellet without forming thin fin or flash of resin on the surface of each electrode portion.
Japanese patent laid-open publication No. 10-313082 (prior art 3) discloses a semiconductor device in which a flat lead frame is used and a semiconductor pellet is mounted on one surface of the lead frame. Also, the lead frame with the semiconductor pellet is resin molded such that the other surface of the lead frame is exposed.
However, when the whole portion of one of the surfaces of the lead frame is exposed from the mold resin, adhesiveness of lead portions and an island portion of the lead frame with the mold resin is deteriorated. Therefore, for example, when the semiconductor device is mounted on a wiring substrate and the like by soldering and the temperature of the lead portions and the island portion rises rapidly, there is a possibility that delamination occurs at the interface portion between the lead frame and the mold resin due to the difference in thermal expansion coefficient therebetween. Thus, it was difficult to maintain high moisture resistance of the semiconductor device.
Therefore, it is an object of the present invention to provide a chip type semiconductor device which is thin and has very small device size.
It is another object of the present invention to provide a chip type semiconductor device which is thin and has very small device size and which has high moisture resistance.
It is still another object of the present invention to provide a chip type semiconductor device which is thin and has very small device size and which can be manufactured easily.
It is still another object of the present invention to provide a chip type semiconductor device which is thin and has very small device size and which has high reliability.
It is still another object of the present invention to provide a chip type semiconductor device which is thin and has very small device size and which can be mounted on a wiring substrate and the like stably.
It is still another object of the present invention to obviate the disadvantages of the conventional chip type semiconductor device which is surface mountable.
According to an aspect of the present invention, there is provided a chip type semiconductor device comprising: an insulating substrate; first and second conductive land areas which are formed on the insulating substrate and which are electrically coupled with each other; a conductive post formed on the first conductive land area; a semiconductor pellet which has electrodes on both sides thereof and which is mounted on the second conductive land area, the electrode on one side of the semiconductor pellet being coupled onto the second conductive land area and the electrode on the other side of the semiconductor pellet having an external electrode electrically coupled thereto; and encapsulation resin portion which encapsulates a main area of the insulating substrate including the conductive post and the semiconductor pellet, wherein top portions of the conductive post and the external electrode electrically coupled to the semiconductor pellet being exposed from the encapsulation resin portion.
In this case, it is preferable that the conductive post and the external electrode electrically coupled to the semiconductor pellet are disposed such that top surfaces of the conductive post and the external electrode become approximately coplanar with each other.
It is also preferable that the conductive post is a column shaped conductive block member.
It is further preferable that the column shaped conductive block member is coupled to the first conductive land area via conductive adhesive.
It is advantageous that the column shaped conductive block member is coupled to the first conductive land area by using ultrasonic bonding.
It is also advantageous that the conductive post comprises a conductive member which is formed by plating.
It is further advantageous that the conductive post comprises a conductive member which is formed by using conductive adhesive.
It is preferable that the first and second conductive land areas are formed by a common conductive land portion which is partitioned by a resist film into the first and second conductive land areas.
It is also preferable that the external electrode electrically coupled with the semiconductor pellet is a flat board shaped conductive member joined onto the electrode of the semiconductor pellet.
It is further preferable that the external electrode electrically coupled with the semiconductor pellet is a hemispherical conductive member joined onto the electrode of the semiconductor pellet.
It is advantageous that the second conductive land area has a concave portion in which the semiconductor pellet is mounted.
According to another aspect of the present invention, there is provided a method of manufacturing a chip type semiconductor device comprising: preparing an insulating substrate; forming first and second conductive land areas on the insulating substrate, the first and second conductive land areas being electrically coupled with each other; forming a conductive post on the first conductive land area; mounting a semiconductor pellet which has electrodes on both sides thereof on the second conductive land area, the electrode on one side of the semiconductor pellet being coupled onto the second conductive land area and the electrode on the other side of the semiconductor pellet having an external electrode electrically coupled thereto; and encapsulating a main area of the insulating substrate including the conductive post and the semiconductor pellet with an encapsulation resin portion, wherein top portions of the conductive post and the external electrode electrically coupled to the semiconductor pellet being exposed from the encapsulation resin portion.
It is preferable that the conductive post and the external electrode electrically coupled to the semiconductor pellet are disposed such that top surfaces of the conductive post and the external electrode become approximately coplanar with each other.
It is also preferable that the conductive post is a column shaped conductive block member and, in the forming a conductive post on the first conductive land area, the column shaped conductive block member is coupled to the first conductive land area via conductive adhesive.
It is further preferable that the conductive post is a column shaped conductive block member and, in the forming a conductive post on the first conductive land area, the column shaped conductive block member is coupled to the first conductive land area by using ultrasonic bonding.
It is advantageous that the conductive post is formed by plating.
It is also advantageous that the conductive post is formed by using conductive adhesive.
It is further advantageous that the first and second conductive land areas are formed by a common conductive land portion which is partitioned by a resist film into the first and second conductive land areas.
It is preferable that the external electrode electrically coupled with the semiconductor pellet is a flat board shaped conductive member joined onto the electrode of the semiconductor pellet.
It is also preferable that the second conductive land area has a concave portion and, in the mounting a semiconductor pellet which has electrodes on both sides thereof on the second conductive land area, the semiconductor pellet is mounted on the concave portion.